(19)
(11) EP 1 777 726 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
21.10.2009 Bulletin 2009/43

(43) Date of publication A2:
25.04.2007 Bulletin 2007/17

(21) Application number: 06022085.2

(22) Date of filing: 20.10.2006
(51) International Patent Classification (IPC): 
H01J 35/06(2006.01)
 H01J 1/16(2006.01)
(84) Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR
Designated Extension States:
AL BA HR MK RS

(30) Priority: 21.10.2005 JP 2005306553
21.10.2005 JP 2005306559

(71) Applicant: Rigaku Corporation
Akishima-shi, Tokyo 196-8666 (JP)

(72) Inventors:
  • Kuribayashi, Masaru
    Akishima-shi Tokyo 196-8666 (JP)
  • Nonoguchi, Masahiro
    Akishima-shi Tokyo 196-8666 (JP)
  • Osaka, Naohisa
    Akishima-shi Tokyo 196-8666 (JP)
  • Kobayashi, Yoji
    Akishima-shi Tokyo 196-8666 (JP)

(74) Representative: Wagner, Karl H. 
Wagner & Geyer Partnerschaft Patent- und Rechtsanwälte Gewürzmühlstrasse 5
80538 München
80538 München (DE)

   


(54) Filament for X-ray tube and X-ray tube having the same


(57) A coiled filament (10) for an X-ray tube has a varied coil pitch to obtain a good uniformity of the longitudinal temperature distribution. The filament has a central region including plural turns having a same coil pitch (p), and end regions which include plural turns each of which has a coil pitch smaller than the coil pitch of the central region. The coil pitches of the plural turns of the end regions are reduced one by one by a same variation (Δp) from a turn close to the central region toward an outermost turn. A value of Δp/p is within a range of 0.015 to 0.1 and k/n is within a range of 0.3 to 0.8, where p is the coil pitch of the central region, Δp is the coil pitch variation of the end regions, n is a total number of turns of the filament, and k is a sum of numbers of turns of the end regions. The k/n preferably satisfies the following equation:









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